Approximately 60% of the nearly 40,000 new cases of hepatitis C (HCV) in the US each year are related to injection drug use (IDU), and IDU is the risk factor for 60% of the 4 million Americans exposed to this virus. The Urban Health Study (UHS) has found that 85-99% of street-recruited IDUs in the San Francisco area have been exposed to HCV. About 75-85% of those exposed will develop chronic hepatitis and are infectious to others, and at least 20% will develop cirrhosis after 2-3 decades. Although IDUs are the risk group most affected by HCV, they are the least likely to be offered HCV treatment due to concerns about medication adherence, side effects, and reinfection. For the past several years, Dr. Sylvestre and her colleagues at OASIS (Organization to Achieve Solutions in Substance-Abuse) have successfully treated nearly 100 methadone patients for HCV using a unique group treatment model that provides ongoing psychological and social support. Dr. Sylvestre has demonstrated that end-of-treatment response (ETR) rates are not significantly different from non-opioid-dependent populations. Drawing on their expertise collecting and analyzing epidemiological data and achieving adherence among HCV+ IDUs, Drs. Karen Seal and Brian Edlin of the Urban Health Study will collaborate with OASIS to extend HCV treatment to street-recruited active IDUs. This pilot feasibility study will use buprenorphine, a new medication for outpatient opioid treatment, to link IDUs to HCV therapy. Active heroin addicts with HCV will be identified through outreach, and after 12-24 weeks of buprenorphine stabilization, compliant participants will undergo pegylated interferon/ribavirin combination therapy while being maintained on buprenorphine. Specifically, in 50 street-recruited heroin injectors stabilized on buprenorphine and undergoing treatment for HCV, this observational feasibility study will describe: 1) the safety, side effects, and dropout rate of pegylated interferon/ribavirin treatment, 2) the adherence to HCV treatment in IDUs as measured by directly observed interferon injections and pill counts, and 3) ETR and sustained virologic responses to HCV treatment. Investigating the feasibility of combined outpatient substance abuse and HCV treatment for active street-recruitedIDUs represents an important step forward in the treatment of HCV and has the promise to decrease the enormous burden of this disease as well as prevent ongoing HCV transmission.